This invention relates generally to digital data storage devices and more particularly to a disc drive having a reduced internal air pressure within the head disc assembly during drive operation.
Disc drives are data storage devices that store digital data in magnetic form on a rotating storage medium on a disc. Modern disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is written to and read from the magnetizable medium on the discs in a plurality of concentric circular tracks typically by an array of transducers mounted on the trailing end of xe2x80x9cheadsxe2x80x9d and carried by a radial actuator assembly for movement of the heads relative to the discs. The read/write transducer, e.g. a magnetoresistive read and inductive write head, is typically used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment.
There is a continual need for higher data capacity in a disc drive in a given form factor, without increasing power consumption or the speed with which data can be transferred to and from the drive. Consequently, disc drive designs particularly focus on ways to achieve higher storage capacity and/or reductions in access times and processing times within the drive. One of the ways to help reduce access and processing time is to increase the spin speed of the drive motor. Today, disc drive speeds 10,000 to 15,000 rpm may be utilized in the drive. As the high end disc drive systems evolve, speeds of up to 25,000 rpm may be utilized. However, when the spin speed is increased, the power consumption of the drive motor increases. This, in turn causes the operating temperatures of the motors to increase, which can be detrimental to operation. This power consumption is partly due to increased windage friction generated by the air/disc interfaces within the drive. More importantly, as the speed increases, the windage induced vibration of the discs increases. Reducing the air pressure reduces the windage induced vibration. Accordingly, there is a need for disc drive data storage device that can efficiently and effectively operate at the higher spin speeds while consuming the same or even less power than in current production disc drives and minimizing the windage induced vibrations.
Against this backdrop the present invention has been developed. The present invention is a disc drive that generates a vacuum within the head disc assembly (HDA) during drive operation. Drawing a vacuum within the HDA permits the disc stack to be rotated at a given speed or angular velocity with lowered windage resistance and thus lower motor power consumption, and helps to lift the heads from the disc surfaces quicker, resulting in less head wear. The reduced air pressure of a vacuum within the HDA will reduce the frictional losses due to drag on the rotating discs permitting the drive to be operated at higher spin speeds without exceeding thermal limitations of the other components of the drive. A preferred embodiment of the present invention is a disc drive incorporating a fan assembly into the disc stack to pump the atmosphere within the drive to the drive exterior and thereby generate a vacuum within the head disc assembly (HDA). The fan assembly includes an impeller disc fastened to the spindle of the disc spin motor, a seal plate extending over the impeller disc and fastened to the base plate of the disc drive, and a discharge passage within the base plate extending through the base plate from a space adjacent a periphery of the impeller disc. A filter covers the discharge passage so that when the drive is de-energized, air returning into the HDA is filtered to prevent intrusion of contaminants.
When the disc drive is de-energized, the internal atmosphere of the HDA returns to equal pressure to the external environment. When the drive is started, the vacuum does not form until the drive is substantially up to speed. Consequently there is a substantial air force against the underside surfaces of the heads, causing them to lift from the landing zone quickly, well in advance of the drive achieving operating speed. This helps to minimize head wear. As drive speed increases, a vacuum is drawn within the HDA such that the heads correctly reposition themselves at a proper flying height above the disc surface for the desired operating speed.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.